Rehabilitation therapies often use physical guidance to assist patients with performing a motor task. Physical guidance or assistance can be given to increase safety, reduce fear, inhibit abnormal movement patterns, or help complete a movement if muscular weakness or incoordination is present. We want to study how assistance affects motor learning of a dynamic walking task. Our overall goal is to determine how the amount, source, and type of assistance used during practice affects motor performance of walking over a narrow balance beam. We propose to use a simple balance assist device to explore assisted motor practice while subjects walk over a narrow balance beam. The balance assist device uses springs to provide a restoring force that directs the pelvis towards the center of the balance beam. The proposed studies will test the hypotheses: 1) subjects that train with the least amount of assistance will perform the balance beam task better than subjects that train with more assistance, 2) subjects that train with self-assistance will perform the task better than subjects that train with no assistance, and 3) subjects that train with error magnification will perform the task better than subjects that train with error reduction. Subjects will train with the balance assist device and we will test their beam walking performance without the device before and after training. We will quantify performance improvement by measuring pelvic lateral motion, co-contraction in lower extremity musculature, and movement time while walking over the beam without assistance. The findings of these studies will lend insight into how physical guidance and assistance should be used in rehabilitation settings and will have significant impact on the design of robotic devices used for rehabilitation. Relevance: We will study how physical assistance affects learning of walking on a narrow balance beam. The results will have applications in the delivery of rehabilitation therapies and in the design of technological devices used for rehabilitation. [unreadable] [unreadable] [unreadable] [unreadable]